What version of Java do I need in order to run my modpack?

I did a fresh install of Windows 10 on my PC the other day. I tried to load up MultiMC (which is the application I create and play my modpacks on) but it said that my Java was either moved or missing or something like that. And when I looked in my "mods" folders, all of the mods (which are .Jar files) didn't appear to have the little Java icon next to them indicating that they where .Jar files. Instead they where just the default note icon you would usually get on a text document file. So I assume from this I don't have Java installed. So I'll have to install it again but I'm not entirely sure what version of Java I should install. Does it depend on the version of Minecraft it is? Or what type of mods I'm using? Or how many mods I'm using? I'd like some suggestions and if it helps I'll list what version of Minecraft I have and the mods I have installed for it. I only use MultiMC to create and play my modpacks with. I do not use the Minecraft or Technic launchers. Also another question I have is, will installing Java again require me to reinstall my mods also? It's just been an awfully long time since I installed Java, I kinda forgot how it all played out

Check these out. If you are confused, it helps to know: what version of Minecraft you are using, and what modloader you are using (Fabric vs Forge). How much RAM your computer has also matters; later modded versions and more/bigger mods need more RAM to run properly.

My computer has 16GB of RAM so would I be okay with that front? Also, the version of Minecraft that is associated with my modpack is 1.7.10 (I have already installed the recommended forge version for it too although I'll have to check back to you on what that forge version is considering I forgot). I have around 40-50 or so mods installed for it at the moment (including all the compatibility and core mods to help the actual mods run). I currently have 5G of RAM allocated to it, but I'm planning on increasing it in future when I add a few more mods. Would Java 8 64 bit be a good option still?

Oh yea, 16GB should be plenty even for modern packs, but for 1.7.10? Yea, Java 8 64-bit is still the way to go.

Edit: Also, maybe press F3 while in-game and see the RAM usage. You may be allocating a lot more RAM than you need for that version and mod count, but then again it varies a lot depending on what kind of mods you have installed, settings, etc.

Ah I see, that's good then. One final question I have is, when I download Java 8 64-Bit, can that mess up any of the .jar files that are already on my PC? And so I'll have to reinstall all of my mods again? Or could I just download Java 8 64-Bit and be ready to play?

Sorry for taking a while to reply.

Edit: Also sorry if I may be asking the sane question twice. Was just wanting to confirm on it.

You do not need to reinstall anything and nothing will be affected; Java is just like a word processing program as far as its "data" (.jar) files are concerned - you don't need to "reinstall" your documents when you install a word processing program! Also, the vanilla launcher downloads its own private version of Java which is invisible to the rest of the system - such a system doesn't need a system-wide installation so .jar files would not be associated with anything; you only really need a system JRE in order to run them directly (i.e. double-click on the file, which won't work for mod jars or even the game itself, which needs a launcher to work. Even then, it is possible to manually associate .jar files with the Minecraft runtime by choosing "open with..." and browsing to its location, same for any other type of file/program (e.g. I associated Notepad with .java files), but either way it isn't needed to run mods unless you are using a .jar installer, e.g. Optifine is packaged as an executable .jar file which includes an installer).